In conventional copying machines in which copying magnification is variable, there is a limit to the maximum and minimum magnification values.
In order to make a copy with a copy magnification over the maximum or minimum magnification values designated in the copying machine (referred to as available magnification limit hereinafter) an original is first copied with the limit magnification, then putting the magnified copy as a secondary original, thereby making another copy which is further magnified. Repeating this operation, a magnified copy with a nearly desired magnification over the limit magnification can be obtained. In the conventional copying machine, however, in making such a magnified copy, the operator must estimate a suitable magnification then set the estimated magnification in the copying machine in each copy, whereby the operation of setting the suitable magnification is much troublesome.